1. Field of the Invention
This invention relates generally to a refrigerant heating type air conditioner, and more specifically to improvements in and relating to the above type of air conditioner in such a way as to provide the least possible refrigerant temperature fluctuation in the indoor side or the inside heat exchanger during a room air heating operation stage of the air conditioner and/or highly adapted for preventing otherwise possible excessive heating of the refrigerant heater, as may frequently occur at the starting-up period of the room air heating operation.
2. Prior Art
As is very well known to those skilled in the art, the delivery side of the refrigerant compressor employed in the system or the above kind of refrigerant heating type room air conditioner is generally connected to the refrigerant heater through the indoor side or the inside heat exchanger, while the outlet side of the said heater is connected with the suction side of the compressor. In this case, the high pressure, high temperature gaseous refrigerant delivered from the compressor has heat released, in the inside heat exchanger, in the form of condensing heat and then, subjected to a pressure reduction by passing through an expansion valve, is returned to the compressor. The liquefied refrigerant is heated up at the refrigerant heater for evaporation. If, at this stage, the temperature of the refrigerant heater should rise excessively, a temperature sensor provided at the outlet side of the refrigerant heater senses this and, in response to the correspondingly changed output signal therefrom, a fuel control valve attached to the heater is caused to close at a predetermined valve closing speed to decrease the fuel gas combustion rate.
In the case of the starting-up operation in the room air heating stage of the refrigerant heating type air conditioner of the above kind, the specific volume of the gaseous refrigerant sucked by the compressor is comparatively large, thus the quantity of refrigerant circulating for practical purposes is correspondingly small, therefore frequent overheating of the refrigerant heater and excessive outlet temperature increase thereat are disadvantageously invited.
Conventionally, such excessive temperature rises as frequently encountered at the refrigerant heater, as described above, are sensed by a temperature sensor provided at the outlet of the refrigerant heater, for controlling the fuel gas combustion rate, as will be described hereinafter more in detail with reference to FIG. 4.
Briefly, in other words, it is necessary to control the ON-OFF operation of the fuel control valve in such a way that when the refrigerant temperature at the refrigerant heater just arrives at a predetermined release operative temperature T1 destined for decreasing the fuel gas combustion rate, the fuel combustion rate reducing operation is introduced, and further, the fuel combustion per se is provisionally ceased when the temperature at the refrigerant heater exceeds a predetermined fuel combustion stopping temperature T0 and finally, the fuel combustion operation is reinstated when the refrigerant heater temperature arrives at a predetermined returning temperature T2.
However, in the case of the aforementioned conventional ON-OFF control mode of the control valve, a grave drawback has been found in that the refrigerant heater temperature cannot rapidly lower as desired, thereby disadvantageously inducing excessive heating of the heater when the fuel gas combustion rate reducing velocity as adopted after the execution of the sensing operation of the release temperature T1 has been conventionally preset to be equal to that in the regular and steady operation of the system, by virtue of a generally large thermal performance demand of the indoor or inside heat exchanger per se, and indeed, in comparison with the generally small amount of refrigerant circulation therethrough at the start-up stage of air heating mode operation of the air conditioner.